Downhole mixing tool

Abstract

A downhole mixing tool and method for removing sand and other debris from a wellbore which combines the sand with a treatment fluid so that the sand is lifted to the surface of the well for removal. The tool includes a chamber into which the sand laden fluid is drawn and the treatment fluid is introduced. Ports into the chamber are arranged to provide a pressure drop to draw the sand laden fluid into the chamber and a mixing time within the chamber before sand laden fluid of lower viscosity exits the chamber to travel to the surface. Additional features include blades on the tool for breaking up obstructions prior to being drawn into the chamber and a lubricating line through the tool to introduce lubricating fluid to the blades.

We claim: 
     
       1. A downhole mixing tool for assisting in sand removal comprising first and second substantially tubular members with at least a portion of the first member being located in the second member; a first end for connection to a tubular string and a second end including one or more inlet ports accessing a chamber formed between the members; the first member including a plurality of treatment ports arranged circumferentially and longitudinally upon its surface; the second member including one or more outlet ports exiting the chamber to an outer surface of the tool; the ports being arranged so that fluid entering the inlet port mixes with treatment fluid introduced to the chamber through the treatment ports and resides in the chamber until the treated fluid exits through the outlet port. 
     
     
       2. A downhole mixing tool according to  claim 1  wherein the second end is tapered and includes one or more blades, each blade being located from an apex of the end towards an edge thereof. 
     
     
       3. A downhole mixing tool according to  claim 2  wherein an inlet port is located relative to each blade. 
     
     
       4. A downhole mixing tool according to  claim 1  wherein the tool includes a third cylindrical member, the third cylindrical member being located through the tool, inside the first member and further including one or more lubricating fluid exit ports arranged upon the second end. 
     
     
       5. A downhole mixing tool according to  claim 1  wherein the treatment ports are located towards the second end of the tool. 
     
     
       6. A downhole mixing tool according to  claim 1  wherein the treatment ports have an aperture which is smaller than the inlet ports. 
     
     
       7. A downhole mixing tool according to  claim 1  wherein the treatment ports are arranged as nozzles to better disperse the treatment fluid into the sand laden fluid. 
     
     
       8. A downhole mixing tool according to  claim 1  wherein the second member includes a plurality of outlet ports arranged circumferentially around its outer surface. 
     
     
       9. A downhole mixing tool according to  claim 1  wherein the outlet ports are substantially greater in aperture than the treatment ports. 
     
     
       10. A downhole mixing tool according to  claim 1  wherein the outlet ports are arranged towards the first end of the tool. 
     
     
       11. A downhole mixing tool according to  claim 1  wherein the members are arranged axially upon the tool creating the chamber in the annulus between the first and second members. 
     
     
       12. A downhole mixing tool according to  claim 11  wherein a first end of the annulus is sealed and a second end of the annulus is formed from the second end of the tool. 
     
     
       13. A downhole mixing tool according to  claim 1  wherein a radius of the first member is less than half a radius of the second member. 
     
     
       14. A method for sand removal from a wellbore, the method comprising the steps:
 a) directing sand laden fluid into a chamber of a tool located in a wellbore, the tool comprising first and second substantially tubular members with at least a portion of the first member being located in the second member; a first end for connection to a tubular string and a second end including one or more inlet ports accessing the chamber formed between the members; the first member including a plurality of treatment ports arranged circumferentially and longitudinally upon its surface; the second member including one or more outlet ports exiting the chamber to an outer surface of the tool; the ports being arranged so that fluid entering the inlet port mixes with treatment fluid introduced to the chamber through the treatment ports and resides in the chamber until the treated fluid exits through the outlet port; 
 b) introducing treatment fluid to the sand laden fluid within the chamber to provide a treated fluid of lower viscosity; 
 c) retaining the treated fluid within the chamber for a period of time; and 
 d) releasing the treated fluid from the tool to travel to the surface for removal of the sand. 
 
     
     
       15. A method according to  claim 14  wherein the method includes the step of breaking up obstructions in the wellbore using the tool. 
     
     
       16. A method according to  claim 14  wherein the method is performed in coiled tubing. 
     
     
       17. A method according to  claim 14  wherein the method includes the step of creating a pressure differential inside the chamber to draw sand laden fluid into the chamber. 
     
     
       18. A method according to  claim 14  wherein the method includes the step of pumping a lubricating fluid through the tool to lubricate the tool for breaking up obstructions.